Compressed gas cylinder connections, which are screwed onto the cylinder valve by means of a coupling nut, serve to link compressed gas cylinders to filling or extraction systems. A connection line leads from the compressed gas cylinder connection to the filling or extraction system. When the compressed gas cylinder is empty, the cylinder valve is closed and the compressed gas cylinder connection is taken away from the cylinder valve. Then, a full compressed gas cylinder is connected and the cylinder valve is opened. After that, gas can continue to be admitted to the filling or extraction system.
This simple exchange of the compressed gas cylinders is not possible with gases that are explosive, self-igniting or especially with toxic gases whose threshold limit values, depending on the medium, are lower than 0.1 ppm. The reason lies in the fact that in the dead spaces, especially between the cylinder valve and the compressed gas cylinder connection as well as in the compressed gas cylinder connection and in the following connection lines themselves, there is still so much gas that it cannot be released to the atmosphere without risk. Therefore, the design of these mechanisms is increasingly being influenced by the necessity of avoiding the risks by means of intensive flushing with a flushing gas. Furthermore, in many cases it is necessary to remove atmospheric air (moisture) that has entered the system by means of flushing, in order to prevent salt formation when corrosive gases are used. For example, it is a generally known measure to equip the cylinder valve with a flushing gas line. In this case, the flushing gas line is then equipped with a flushing valve (West German Pat. No. 36 22 527).
According to West German Utility Model No. 86 22 871, the proposal is made to equip the compressed gas cylinder connection with a flushing gas line. The flushing gas line is connected to a flushing gas supply via a flushing connection.
However, the flushing gas has to flow via these flushing gas connections into the flushing gas line and it has to continue to flow via the extraction borehole of the cylinder valve into the adjacent connection lines and fittings, until the entire process gas has been displaced.